Method of plasma etching

ABSTRACT

A method of plasma etching which comprises introducing a gas containing C x F y  (X≧2) and CF 4  into a treatment chamber, and forming a plasma of the gas, to thereby subject a coating film in an article to be treated (W) being present in the treatment chamber to plasma etching through a pattern having openings placed on the coating film. The method can be used for carrying out plasma etching with the suppression of etching-stop phenomenon and without the formation of deposits in an etching hole.

FIELD OF THE INVENTION

The present invention relates to a plasma etching method to be used in the manufacturing process of semiconductor devices.

BACKGROUND OF THE INVENTION

Conventionally, a gas containing fluorocarbon as a major component has been used as etching gas to plasma etch a SiO₂ film disposed on a substrate to be processed through a pattern of openings in a photoresist.

However, when the gas having fluorocarbon as a major component is used, by-products tend to accumulate in the holes during an etching process and the etching rate would slow down, thereby inducing a so-called etch stop at which point the etching process is finally terminated. Such tendency to induce an etch stop significantly increases when the hole has a diameter in the order of submicrons and thereby failing to provide microprocessing capability in accordance with the recent demands.

Therefore, in order to prevent such an etch stop, adding oxygen to etching gas has been attempted to suppress the formation of by-products in the hole.

However, recently, instead of photoresist, hard mask etching by using metal or metal nitride mask has been employed widely. When a gas containing fluorocarbon and oxygen is used in etching SiO₂ with metal or metal nitride as a mask, it is problematic that metal oxide deposits are formed in etching holes. Such deposits cannot be removed even by a wet cleaning process. Further, when plasma processing is performed by using a gas containing Cl, the deposits can be removed but the hard mask is etched at the same time.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a plasma etching method for performing a plasma etching without generation of deposits in an etching hole while preventing the etching stop.

In accordance with the present invention, there is provided a plasma etching method including the step of plasma etching a film on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the film by converting a gas containing C_(x)F_(y)(X≧2) and CF₄ introduced into the treatment chamber to a plasma.

The metal compound may be a metal nitride. The metal nitride may be TiN or TaN.

The gas containing C_(x)F_(y) (X≧2) and CF₄ may also include N₂. Further, the gas may also include Ar.

The film on the article to be treated may be a SiO₂ film, a SiC film or a SiOC film. SiOC used herein represents a so-called organic silicon oxide which includes a main chain of —Si—O— and has an organic functional group such as a methyl group at least at a portion of side chains.

C_(x)F_(y) (X≧2) of the gas may be C₄F₆. In such a case, the gas preferably has a ratio of C₄F₆ flow rate to CF₄ flow rate (C₄F₆ flow rate/CF₄ flow rate) in the range from 0.12 to 0.20. That is because etching stop occurs if the ratio is greater than 0.20, and deposits (even a few) are formed in a hole or selectivity of an etching target film to a mask (etching rate of the film/etching rate of the mask) becomes decreased if the ratio is less than 0.12. C_(x)F_(y) (X≧2) of the gas may be C₄F₈ or C₅F₈.

In accordance with the present invention, there is provided a plasma etching method including the step of plasma etching a SiO₂ film disposed on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the SiO₂ film by converting a gas containing C₄F₆ and N₂ introduced into the treatment chamber to a plasma.

Further, in accordance with the present invention, there is provided a plasma etching method including the step of plasma etching a SiC film disposed on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the SiC film by converting a gas containing C₄F₆ and N₂ introduced into the treatment chamber to a plasma.

Furthermore, in accordance with the present invention, there is provided a plasma etching method including the step of plasma etching a SiOC film disposed on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the SiOC film by converting a gas containing C₄F₆ and N₂ introduced into the treatment chamber to a plasma.

The metal compound may be a metal nitride. The metal nitride may be TiN or TaN.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic cross sectional view of a plasma etching apparatus to which the present invention can be applied; and

FIG. 2 shows a cross sectional view of an etching target portion of an article to be treated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a schematic cross sectional view of a plasma etching apparatus 1 to which the present invention is applied. A frame grounded treatment chamber 2 is formed of metal, e.g., aluminum of which surface is oxidized. Inside the treatment chamber 2, installed on the bottom portion thereof is a susceptor 5, which functions as a lower electrode of parallel plate electrodes via an insulator 3. A high pass filter (HPF) 6 is connected to the susceptor 5.

Installed on the susceptor 5 is an electrostatic chuck 11 on which an article W to be treated such as a semiconductor wafer is mounted. The electrostatic chuck 11 has an electrode 12 embedded in an insulator, wherein the electrode 12 is connected to a DC power supply 13 which applies a DC voltage to the electrode 12 so that the electrostatic chuck 11 electrostatically attracts and holds the article W to be treated thereon. Further, a focus ring 15 is placed to surround the article to be treated W. The focus ring 15 is made of Si, SiO₂ or the like, and improves etching uniformity.

Further, placed above the susceptor 5 is an upper electrode 21 facing the susceptor 5. The upper electrode 21 is installed at the upper portion of the treatment chamber 2 through an insulator 22 and includes a showerhead-shaped electrode plate 24 and a supporting body 25 for holding the electrode plate 24 in place.

A gas inlet opening 26 is provided in the central portion of the supporting body 25 and is connected to a gas supply line 27, a valve 28, a mass flow controller 29 and an etching gas source 30 in the order provided. The etching gas source 30 supplies a gas, for example, C_(x)F_(y) (X≧2), CF₄, N₂, Ar and the like. C_(x)F_(y) (X≧2) is C₄F₆, C₄F₈, C₅F₈, and the like. Further, in case of using C₄F₆, it is preferable that a ratio of C₄F₆ flow rate to CF₄ flow rate (C₄F₆ flow rate/CF₄ flow rate) is 0.12 to 0.20. In case of using C₄F₆, N₂ can be used in lieu of CF₄.

In this case, connected to the bottom portion of the treatment chamber 2 is a gas exhaust line 31 which is connected to a gas exhaust unit 35. Further, a gate valve 32 is disposed in a sidewall of the treatment chamber 2, wherein the article W to be treated is transported between the treatment chamber 2 and a neighboring load-lock chamber (not shown) through the valve.

Connected to the upper electrode 21 are a low pass filter (LPF) 42 and a first high frequency power supply 40 via a matching unit 41, respectively. A second high frequency power supply 50 is connected to the susceptor 5 serving as the lower electrode via a matching unit 51.

Hereinafter, a plasma etching process using the aforementioned plasma etching apparatus 1 will be described in detail, wherein a SiO₂ film on the article to be treated is plasma etched through a pattern of openings of a mask. In this case, as shown in FIG. 2, there will be described a case where a SiO₂ film 62 formed on a SiN film 61 is plasma etched through a pattern of openings of a TiN mask 63.

Upon opening the gate valve 32, the article W to be treated is loaded into the treatment chamber 2 and mounted on the electrostatic chuck 11. Next, the gate valve 32 is closed and the treatment chamber 2 is depressurized by the gas exhaust unit 35. Then, after opening the valve 28, from the etching gas source 30, the above etching gas, e.g., an etching gas containing C₄F₆, CF₄, and Ar or an etching gas containing C₄F₆, N₂, and Ar, is supplied.

Under such conditions, a high frequency power is supplied from the high frequency power supply to the upper electrode 21 and to the susceptor serving as the lower electrode, and the SiO₂ film 62 on the article W to be treated is etched by converting the etching gas into a plasma. In this case, before or after applying the high frequency power to the upper and the lower electrode, a DC voltage is applied from the DC power supply 13 to the electrode 12 inside the electrostatic chuck 11 to thereby electrostatically attracts and holds the article W to be treated on the electrostatic chuck 11.

During the etching process, a predetermined emission intensity is detected by an endpoint detector (not shown) and the etching process is terminated based on the detected value.

In the present embodiment, as described above, by using a gas containing C_(x)F_(y) (X≧2) and CF₄, or a gas-containing C₄F₆ for C_(x)F_(y) and N₂ instead of CF₄, the SiO₂ film 62 is etched through the TiN mask 63 such that it is possible to form etching holes without the generation of deposits in the etching holes and without the occurrence of an etching stop.

Further, an etching target is not limited to a SiO₂ film and, particularly, in case the film is formed of at least one component from SiO₂, SiC and SiOC, the above results are more readily obtainable. Further, instead of using TiN as the mask, TaN or other metal nitride is also acceptable as a mask material. In addition, the configuration of the etching apparatus is not limited to that shown in FIG. 1.

Embodiments

Hereinafter, preferred embodiments of the present invention will be described.

-   -   Frequency of high frequency power supply applied to upper         electrode: 60 MHz     -   High frequency power applied to upper electrode: 1000 W     -   Frequency of high frequency power supply applied to lower         electrode: 2 MHz     -   High frequency power applied to lower electrode: 800     -   Temperature of susceptor: 40° C.     -   Pressure in treatment chamber: 6.65 Pa (50 mTorr)     -   Flow rate of etching gas: C₄F₆ is 0.018 L/min(18 sccm); CF₄ is         0.1 L/min (100 sccm); and Ar is 0.6 L/min (600 sccm).

Under the above process conditions, as shown in FIG. 2, a SiO₂ film formed on a silicon wafer was etched through a pattern of openings of a TiN mask.

As a result, deposits were not formed in etching holes and, further, an etching stop did not occur.

Further, in case of etching with C₅F₈ substituting C₄F₆ in the etching gas in the above embodiment, likewise, it was possible to perform etching without the formation of deposits in etching holes and without the occurrence of etching stop as well.

Further, in case of etching with N₂ substituting CF₄ in the etching gas and doubling the flow rate, i.e., 0.2 L/min (200 sccm) in the above embodiment, similarly, it was possible to perform etching without the formation of deposits in etching holes and the occurrence of etching stop.

As described above, in accordance with the present invention, a film such as a SiO₂ film patterned by metal compound such as metal nitride is etched by a plasma generated from a gas containing C_(x)F_(y) (X≧2) and CF₄, or a gas containing C₄F₆ and N₂, whereby it is possible to prevent etching stop and form etching holes without the generation of deposits in the etching holes.

While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be without departing from the spirit and scope of the invention as defined in the following claims. 

1. A plasma etching method comprising: plasma etching a film on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the film by converting a gas containing C_(x)F_(y) (X≧2), CF₄ and N₂ introduced into the treatment chamber to a plasma.
 2. The plasma etching method of claim 1, wherein the metal compound is a metal nitride.
 3. The plasma etching method of claim 2, wherein the metal nitride is TiN.
 4. The plasma etching method of claim 2, wherein the metal nitride is TaN.
 5. (canceled)
 6. The plasma etching method of claim 1, wherein the gas further includes Ar.
 7. A plasma etching method comprising: plasma etching a SiO₂ film on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the film by converting a gas containing C_(x)F_(y) (X≧2) and CF₄ introduced into the treatment chamber to a plasma.
 8. A plasma etching method comprising: plasma etching a SiC film on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the film by converting a gas containing C_(x)F_(y) (X≧2) and CF₄ introduced into the treatment chamber to a plasma.
 9. A plasma etching method comprising: plasma etching a SiOC film on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the film by converting a gas containing C_(x)F_(y) (X≧2) and CF₄ introduced into the treatment chamber to a plasma.
 10. A plasma etching method comprising: plasma etching a film formed of one among SiO₂, SiC and SiOC on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the film by converting a gas containing C₄F₆ and CF₄ introduced into the treatment chamber to a plasma.
 11. The plasma etching method of claim 10, wherein the gas has a ratio of C₄F₆ flow rate to CF₄ flow rate (C₄F₆ flow rate/CF₄ flow rate) in the range from 0.12 to 0.20.
 12. The plasma etching method of claim 1, wherein C_(x)F_(y) (X≧2) of the gas is C₄F₈.
 13. A plasma etching method comprising: plasma etching a film on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the film by converting a gas containing C₅F₈ and CF₄ introduced into the treatment chamber to a plasma.
 14. A plasma etching method comprising: plasma etching a SiO₂ film disposed on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the SiO₂ film by converting a gas containing C₄F₆ and N₂ introduced into the treatment chamber to a plasma.
 15. A plasma etching method comprising: plasma etching a SiC film disposed on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the SiC film by converting a gas containing C₄F₆ and N₂ introduced into the treatment chamber to a plasma.
 16. A plasma etching method comprising: plasma etching a SiOC film disposed on an article to be treated accommodated in a treatment chamber through a pattern of openings of a mask made of a metal compound formed on the SiOC film by converting a gas containing C₄F₆ and N₂ introduced into the treatment chamber to a plasma.
 17. The plasma etching method of claim 14, wherein the metal compound is a metal nitride.
 18. The plasma etching method of claim 17, wherein the metal nitride is TiN.
 19. The plasma etching method of claim 17, wherein the metal nitride is TaN.
 20. The plasma etching method of claim 7, wherein C_(x)F_(y) (X≧2) of the gas is C₄F₈.
 21. The plasma etching method of claim 8, wherein C_(x)F_(y) (X≧2) of the gas is C₄F₈.
 22. The plasma etching method of claim 9, wherein C_(x)F_(y) (X≧2) of the gas is C₄F₈. 